1. Field of the Invention
The present invention relates to an optical communication system, and is more particularly related to a receiver transponder to be used in an optical add/drop node.
2. Discussion of the Background
Network availability is of significant importance in today""s telecommunication systems and data communication networks. One way of improving the availability of such networks involves building protection features into the networks such that efficient means are provided to switch traffic to a different path in the case of a link or component failure along the original path. With the rapid development of DWDM (Dense Wavelength Division Multiplexing) systems and research of general and special techniques of building optical networks using different forms of WDM (Wavelength Division Multiplexing) systems generally, there is a growing interest in developing an approach to handle protection in optical transmission systems and optical networks.
It is an object of the invention to provide an optical add/drop node comprising a receiver transponder which has switching capabilities with a high reliability and which can be easily monitored.
According to one aspect of the invention, a receiver transponder used in an optical add/drop node comprises a plurality of optoelectric converters that are configured to convert received optical signals to electric signals. A first one of the optoelectric converters is connected to an optical fiber carrying light signals from a first direction. A second one of the optoelectric converters is connected to another optical fiber carrying light signals from a second direction opposite the first direction. An electronic switch is coupled to the plurality of optoelectric converters and has a plurality of input terminals, a signal output terminal, and a control input terminal. Each of the first and second optoelectric converters has output terminals that are connected to the input terminals of the electronic switch. The control input terminal receives a signal to control the electronic switch to select one of the input terminals from which one of the electric signals is switched to the signal output terminal. The above arrangement advantageously provides a cost effective optical network protection system.
According to another aspect of the invention, a protected network comprises a first optical fiber path carrying light signals in a first direction, and a second optical fiber path carry light signals in a second direction that is opposite the first direction. A plurality of optical add/drop nodes are coupled to the first optical fiber path and the second optical fiber path to form a ring configuration. Each of the optical add/drop nodes includes a receiver transponder that has a plurality of optoelectric converters, which are configured to convert received optical signals to electric signals. A first one of the optoelectric converters is connected to the first optical fiber path, and a second one of the optoelectric converter is connected to the second optical fiber. Each of the optical add/drop nodes also includes an electronic switch that is coupled to the plurality of optoelectric converters. The electronic switch has a plurality of input terminals, a signal output terminal, and a control input terminal. Each of the first and second optoelectric converters has output terminals that are connected to the input terminals of the electronic switch. The control input terminal receives a signal to control the electronic switch to select one of the input terminals from which one of the electric signals is switched to the signal output terminal. Under this approach, a reliable optical protection scheme is achieved.
According to yet another aspect of the invention, a receiver transponder used in an optical add/drop node comprises a plurality of converter means for converting received optical signals to electric signals. A first one of the converter means is connected to an optical fiber carrying light signals from a first direction. A second one of the converter means is connected to another optical fiber carrying light signals from a second direction opposite the first direction. A switching means is coupled to the plurality of optoelectric converters and has a plurality of input terminals, a signal output terminal, and a control input terminal. Each of the first and second converter means has output terminals that are connected to the input terminals of the switching means. The control input terminal receives a signal to control the switching means for selecting one of the input terminals from which one of the electric signals is switched to the signal output terminal. The above arrangement advantageously provides a simple way to monitor signals within an optical network with protection capability.